Amedee

I just did a quick check and it is indeed around 70mm. I just used an M3 rod which I cut at the desired length. On one side I have a NylStop nut glued with green Loctite (it is the top side you can see on the pictures).

25% infill

Mmmmh... You might have scaling issues with your printer, I checked the model and the outer diameter is already 16.2mm See: https://images2.imgbox.com/24/15/VBIpdQkw_o.png I am happy to make an version for you, but you would need to tell me how much bigger it needs to be. Also I am not sure to understand how suppressing the chamfer would make it easier, it can only make it harder (but we might not talk about the same chamfer ;) ) Note that you will need a very tight fit to avoid any movement of the head in the mount. The bottom-middle part is just there to keep the head in place horizontally, there should be no need to press: the head won't move up/down as it is locked in the groove. For my printer, I initially printed in nGen as first iteration, and used it to print a new one in PolyCarbonate. For the final one, I think I filed a bit the groove to have a smooth fit, and added epoxy glue to avoid any play -- just to be sure (there was some play at the end with the nGen version, but I guess printing 280°C+ was a bit too hot for the nGen...)

It is not an OpenSCAD project -- I just referenced the OpenSCAD project that inspired me. If you want to modify, the original STEP file is already uploaded.